This container exposes the app on port 3000 by default, so you will need to map that port to whatever port you want for your deployment. The example above maps port 80 on your host to port 3000 on the container (-p 80:3000). Also note that we haven't specified a MONGO_URL above, so the container will use an internal Mongo database. This isn't recommended for production deployments, but it's fine for testing. To specify an external database, all you need to do is add the MONGO_URL environment variable: